APOE and early-onset autosomal dominant Alzheimer disease: Results from cross-sectional studies have been mixed, with some finding higher WMH burden48,49 and lower volumes or thinner cortex23,50-53 among individuals at greater Alzheimer’s disease-genetic risk (i.e. APOE-ɛ4 carriers and/or higher AD-PRS), and others not finding such differences.23,54-59 For APOE-ɛ2 genetic status, results from cross-sectional studies have also been mixed.22,52,54,60,61 Few prior longitudinal studies have been conducted among cognitively unimpaired older individuals.